Effects of High-Salinity Domestication Gradient, Speed, and Mode on Weight Gain, Activity, and Survival Rate of Litopenaeus vannamei Postlarvae

Abstract:

To investigate the optimum high-salinity domestication gradient, speed, and mode of Litopenaeus vannamei postlarvae, a salinization experiment was designed. Salinity increased from 30 to 60. Different high-salinity domestication gradients (3/d, 6/d, 9/d, 12/d, and 15/d), speeds (1, 3, 6, 12, and 18 h/time), and modes (early salinization, medium-term salinization, later salinization, and interval salinization) were used. The weight gain, activity, and survival rate of L. vannamei postlarvae were tested during high-salinity domestication. The results showed that the different high-salinity domestication gradients, speeds, and modes had significant effects on the weight gain, activity, and survival rate of postlarvae (P<0.05). The optimal high-salinity domestication gradient was 3~6/d; the survival rate of postlarvae remained at 74.07% to 78.83% in this gradient. When the high-salinity domestication gradient exceeded 9/d, the survival rate of postlarvae decreased sharply (P<0.05), and was only 43.37% in the high-salinity domestication gradient of 15/d. In addition, the rapid high-salinity domestication speed decreased the survival rate and activity. When the domestication speed was faster than 1 h/time, the survival rate of postlarvae was reduced to nearly 50%; as the domestication speed decreased, the growth rate of postlarvae increased. When the high-salinity domestication speed was 6~18 h/time, the daily weight gain of postlarvae was stable at 1.48~1.51 mg. The later salinization and interval salinization were superior to the early salinization and medium-term salinization regarding the postlarvae activity and survival rate, the postlarvae activity was as follows: interval salinization>later salinization>medium-term salinization>early salinization. Overall, the optimal high-salinity domestication gradient was 3~6/d, the best high-salinity domestication speed was 6~12 h/time, which will help postlarvae to reach the scheduled standard and achieve the target weight gain with later salinization and interval salinization.